was Charles Darwin
's hypothetical mechanism for heredity
. He presented this 'provisional hypothesis' in his 1868
work The Variation of Animals and Plants Under Domestication
and felt that it brought 'together a multitude of facts which are at present left disconnected by any efficient cause'. The etymology of the word comes from the Greek
(a prefix meaning "whole", "encompassing") and genesis
(birth) or genos
Pangenesis holds that body cells shed gemmules, which collect in the reproductive organs prior to fertilization. Thus every cell in the body has a 'vote' in the constitution of the offspring. Atavisms arise due to the awaking of long-dormant gemmules, while limbs regenerate due to the activation of gemmules from the missing limb.
Pangenesis itself is now seen as deeply flawed and not supported by observation, yet it represents Darwin's attempt to explain such diverse phenomena as:
In his later work, The Descent of Man, Darwin elaborated further on the model. In a section on the "Laws of inheritance," Darwin specified that two elements in particular were most important: the transmission and the development of inherited characteristics. Darwin's insights were that characteristics could be transmitted which were not at the time of transmission actually being manifest in the parent organism, and that certain traits would manifest themselves at the same point of development (say, old age) in both the parent and child organisms. In order to make sense of his theory of sexual selection, he also stipulated that certain traits could be passed through organisms but would only develop depending on the sex of the organism in question.
Galton's experiments on rabbits
Darwin's half-cousin Francis Galton
conducted wide-ranging inquiries into heredity which led him to refute Charles Darwin's hypothetical theory of pangenesis. In consultation with Darwin, he set out to see if gemmules
were transported in the blood. In a long series of experiments in 1869 to 1871, he transfused the blood between dissimilar breeds of rabbits, and examined the features of their offspring
He found no evidence of characters transmitted in the transfused blood . Darwin challenged the validity of Galton's experiment, giving his reasons in an article published in 'Nature'
where he wrote: "Now, in the chapter on Pangenesis in my "Variation of Animals and Plants under Domestication," I have not said one word about the blood, or about any fluid proper to any circulating system. It is, indeed, obvious that the presence of gemmules in the blood can form no necessary part of my hypothesis; for I refer in illustration of it to the lowest animals, such as the Protozoa, which do not possess blood or any vessels; and I refer to plants in which the fluid, when present in the vessels, cannot be considered as true blood." He goes on to admit: "Nevertheless, when I first heard of Mr. Galton's experiments, I did not sufficiently reflect on the subject, and saw not the difficulty of believing in the presence of gemmules in the blood."